Editing Dickcissel (section)

==="Townsend's dickcissel"===
[[File:Spiza townsendi.jpg|upright|thumb|left|Lithograph of "Townsend's Bunting"]]
A problematic specimen is often discussed under the name of '''''Spiza townsendi''''' (or ''Spiza townsendii'', the original misspelt [[specific name (zoology)|specific name]] proposed by [[John James Audubon]]). This individual was collected on May 11, 1833, by Audubon's colleague [[John Kirk Townsend]] in [[New Garden Township, Pennsylvania|New Garden Township]], [[Chester County, Pennsylvania]].<ref>{{cite book | last=Audubon | first=John James | author-link=John James Audubon | year=1834 | chapter=Townsend's Bunting | title=Ornithological Biography, or an account of the habits of the birds of the United States of America | volume=2 | location=Edinburgh | publisher=Adam Black | pages=183–184 | chapter-url=https://www.biodiversitylibrary.org/page/33239545 }}</ref><ref>{{ cite book | last=Audubon | first=John James | author-link=John James Audubon | year=1841 | chapter=Townsend's Bunting | title=The Birds of America, from drawings made in the United States and their territories | volume=3 | location=New York | publisher=J.B. Chevalier | page=62, Plate 157 | chapter-url=https://www.biodiversitylibrary.org/page/40383836 }}</ref><ref>{{ cite book | last=Ridgway | first=Robert | year=1901 | author-link=Robert Ridgway | chapter=''Spiza townsendii'' (Audubon) | title=The Birds of North and Middle America | series=Bulletin of the United States National Museum. Volume 50, Part 1 | place=Washington | pages=174–175 | chapter-url=https://www.biodiversitylibrary.org/page/7514987 }}</ref> The specimen remains unique and nothing is known about what it represents with certainty; it had thus even been suggested to be an [[extinct]] relative. In 2014, Kyle Blaney photographed the bird in Ontario, proving its continuing existence.<ref>{{Cite news|url=http://blog.aba.org/2014/09/open-mic-the-townsends-bunting-story.html|title=Open Mic: The Townsend's Bunting Story |date=2014-09-18|work=ABA Blog |access-date=2017-06-25|language=en-US}}</ref>

It is commonly called "Townsend's dickcissel" (or "Townsend's bunting", "Townsend's finch"<ref>[http://avibase.bsc-eoc.org/species.jsp?lang=EN&avibaseid=E698E65AF4668388 ''Spiza townsendi'']. Avibase</ref>) in reference to the collector whom the scientific name honors. Rather than a distinct species or subspecies, it is (as certainly as this can be said in absence of direct proof) a color [[variant (zoology)|variant]]. Comparing the birds, it is immediately obvious that the yellow [[lipochrome]] [[pigment]]s are entirely absent in "Townsend's dickcissel". The specimen has [[foxing|foxed]] today, giving it an altogether beige hue, but when originally shot, the olive areas of the head were grey as the cheeks, and the yellow and buff on face and underside was pure white. The brown wings and tail were rufous, due to the [[pheomelanin]]s not being tinged by lipochromes.

Thus, this bird is very likely certainly the result of a simple genetic change, perhaps just a single [[point mutation]], affecting some part of the [[carotinoid]] [[metabolism]] – essentially the same thing that happens in [[albinism]], but in a different [[metabolic pathway]]. Though the bird seemed to be healthy and had survived to maturity when it found its untimely end through Townsend's gun, no other such specimens have been documented before, nor ever since. Albinism and other pigment aberrations are not infrequently seen in birds, and the lack of further specimens is somewhat puzzling in that respect.

No specific details are known about the dickcissel's lipochrome metabolism; it may be more fine-tuned than in other birds, so that most mutations therein will be lethal and Audubon's bird was simply one of the very few individuals that survived. In wild birds, varying from species to species, some color aberrations are less frequently seen than others, and in captive birds such as [[domestic canary|canaries]], some color mutations have only arisen a handful of times at most during several centuries of dedicated breeding and screening for novel color variants (see also [[Budgerigar colour genetics]]). While only a complete [[molecular biology|molecular biological]] study of the dickcissel's metabolism and the specimen's [[ancient DNA]] stands any reasonable chance to resolve the question with certainty, the hypothesis of an extremely uncommon color mutation is plausible, and such phenomena certainly occur in other [[Passeroidea]].

Alternatively, the bird was considered a [[hybrid (biology)|hybrid]], but the present state of knowledge of the dickcissel's relations makes this not very plausible; a number of species exist with which ''Spiza'' could conceivably produce hybrids, such as ''Passerina'', but the lack of even the slightest hint of blue structural colors in Townsend's specimen and it moreover being not different from a dickcissel in [[Morphology (biology)|habitus]] makes the hybrid theory suspect. Regardless, Townsend observed the bird making vocalizations reminiscent more of an [[indigo bunting]] (''Passerina cyanea''), and by comparing [[mtDNA|mitochondrial]] and [[nuclear DNA]] sequences of the specimen with those of the dickcissel, the indigo bunting, and perhaps other ''Passerina'', the hybridization hypothesis should be far more easy to prove or reject than a color aberration. On the other hand, not enough is known on whether dickcissels pick up their characteristic vocalizations from conspecific males or whether they are innate, thus no firm conclusion regarding Townsend's observations has been made.